|Beirn, Lisa - Rutgers University|
|Meyer, William - Rutgers University|
|Clarke, Bruce - Rutgers University|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2015
Publication Date: 10/14/2015
Citation: Beirn, L.A., Meyer, W.A., Clarke, B.B., Crouch, J.A. 2015. A greenhouse-based inoculation protocol for fungi causing crown rust and stem rust diseases of Kentucky bluegrass turf. HortScience. 50(10):1509-1513.
Interpretive Summary: Rusts are fungal diseases that destroy many plants. Rust diseases are disfiguring and very damaging to popular grasses such as Kentucky bluegrass. Kentucky bluegrass is extensively grown as turfgrasses in athletic fields, golf courses, and lawns, and commercially by sod and grass seed producers. The best way to minimize damage due to rusts is to identify grasses that are not easily infected by the rust fungus. Turfgrass breeders typically identify these disease resistant grasses by screening them in outdoor field plots, a time-consuming and expensive process. In this work, we developed and tested a new and reliable method to infect Kentucky bluegrass plants with two types of fungi that cause rust diseases. This method can be performed indoors under controlled environmental conditions, and is a way to quickly identify plants that are easily infected by the rust fungus. With this ability to perform pre-screening of Kentucky bluegrass in greenhouses, turfgrass breeders will be able to remove the plants most affected by rust diseases. Removal of these plants can be done in advance of expensive field tests, saving time and money.
Technical Abstract: Rusts are destructive fungal diseases that can cause severe thinning and unattractive discoloration of kentucky bluegrass (KBG; Poa pratensis L.). Currently, turfgrass breeding programs rely on field evaluations to screen KBG germplasm for rust resistance; methods that are expensive, labor intensive, and require large turf areas. The availability of a greenhouse-based assay to perform prescreening of KBG germplasm for resistance to rust diseases before field trials would allow breeders to remove the poorest performing plants before field evaluations thus enhancing breeding efficiency. In this study, we set out to develop a reliable, low-cost greenhouse inoculation protocol for the two most common rust pathogens of KBG in temperate growing regions: Puccinia coronata and Puccinia graminis, the causal agents of crown and stem rust, respectively. Using a modified inoculation assay and custom-built plexi-glass chambers adapted from protocols used for cereal rust pathogens, urediniospores of crown and stem rust fungi developed on inoculated plants 10 to 14 days postinoculation. Real-time polymerase chain reaction (PCR) assays, disease symptomology, and morphology of urediniospores confirmed the presence and identity of both rust pathogens from inoculated host tissue. The inoculation protocols described here represent an effective method to accelerate screening of KBG germplasm for resistance to crown and stem rust diseases. Infection of KBG plants in the greenhouse will also allow breeders to maintain populations of crown and stem rust fungi throughout the year, providing a reliable and ongoing source of pathogen inoculum for experimentation and screening in the future.